In every vehicular air conditioning system there is a plurality of sections of flexible hose. These hose sections connect in a single system, with various system components including a compressor, condenser, evaporator and other system components.
A coupling is required at each hose end to allow the hose to be secured to the various components between which it extends. The coupling will usually include the end portion of a rigid tube which is secured to the flexible hose. The tube will include a flare fitting or other arrangement for connection to a system component.
The usual coupling for securing the flexible hose to the rigid tube is to utilize a connector portion with two concentric cylindrical walls spaced from one another by approximately the thickness of the hose. One of these concentric walls includes a radially extending flange securing it to the other. The inner concentric wall includes a throughbore to allow for fluid passage between the rigid tube and hose.
The hose is inserted between the inner concentric cylinder and the outer concentric cylinder. The outer cylindrical wall is crimped (plastically deformed) onto the hose and the inner concentric cylinder to form a fluid tight joint.
A typical coupling of this type is shown in U.S. Pat. No. 5,044,671, assigned to TI Group Automotive Systems, LLC. There, the inner cylindrical wall is formed by the outer surface of the rigid tube. The outer concentric wall is formed by a sleeve that includes a radial flange extending radially inward and joined to the inner concentric tube. The inner concentric wall, or tube, is provided with annular locking ribs and the radial flange is the swaged or crimped onto the locking ribs of the tube.
Alternatively, the tube may be upset, or otherwise provided with a radial shoulder, immediately adjacent and contiguous with both sides of the radial flange of the sleeve to provide an axial stop in both directions. In each case, the axial position of the two coupling components, (i.e., the sleeve and the tube) is fixed to define an annular space to receive the hose. This type of coupling configuration requires a number of metal forming operations on the end of the tube and a separately formed sleeve.
A more recent development in tube to house couplings is described in U.S. Pat. No. 5,417,461 also assigned to TI Group Automotive Systems, LLC. Here, the outer cylindrical crimp wall is integral with the rigid tube. The inner coupling wall is defined by a separate insert fitted with a seal. The tube is preformed to include a circumferential seat to mate with the installed seal on the insert.
Another similar coupling is described in U.S. Pat. No. 5,961,157, assigned to Manuli Auto France. This patent discloses a coupling in which the outer cylindrical crimp wall is also formed by the rigid tube. The inner cylindrical wall is defined by an insert assembled into the tube end to define the hose receiving annulus. The insert is also fitted with a seal. In this design, a forward tubular portion of the insert, fitted with a seal, is forced into the unexpanded inner diameter end portion of the rigid tube. Necessarily the diameter of the throughbore of the insert is smaller than the bore of the tube.
The insert in each of the foregoing designs typically is made from a rigid material (such as aluminum or steel) having sufficient strength to resist the crimping forces necessary to create a seal between the insert and the flexible hose. These materials and associated manufacturing methods are costly. One solution would be to reduce the crimping force and fit the insert with a seal member such as the O-ring employed between the rigid tube and the insert. Such a seal member would create a seal between the outer surface of the insert and the inner diameter of the flexible hose. The required groove to retain the seal would require an increase in wall thickness of the insert and therefore a reduced throughbore diameter. Such a reduced throughbore has negative effects on the performance of the coupling with regard to fluid flow since it defines a restrictive orifice in the fluid system.
The present invention provides a coupling device and method of making a connection between a rigid tube and flexible hose which avoids undue restriction of the flow passage and simplifies manufacturing processes required to create the coupling.